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wavelength-imaging.md
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......@@ -26,18 +26,12 @@ There are two choices to record a image for [position detection](https://git-xen
## 3. Rotation tracking and light color
The rotation of the discs can be tracked by drawing a ultra-violet(UV) sensitive bar on them. Tracking the rotation of the bars is equal to tracking the rotation of the particles. Those labels are only visible under UV light so they will not interference with the photoelastic fringes. The right figure below shows an image taken under UV light that shows all the UV bars on them. (from [*J. Ren et al.*](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.018302)) The UV bars are plotted using [*MAR-C0 Invisible Blue UV Pen from Risk Reactor*](http://www.riskreactor.com/invisible-uv-pens/mar-c0-invisible-blue-uv-marking-pens/) (left figure). UV labels can also be used to help finding the center of non-spherical particles, where Hough transformation for particle boundary detection does not work.
The rotation of the discs can be tracked by drawing a ultra-violet(UV) sensitive bar on them. Tracking the rotation of the bars is equal to tracking the rotation of the particles. Those labels are only visible under UV light so they will not interference with the photoelastic fringes. The right figure below shows an image taken under UV light that shows all the UV bars on them. (from [*J. Ren et al.*](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.018302)) The UV bars are plotted using [*MAR-C0 Invisible Blue UV Pen from Risk Reactor*](http://www.riskreactor.com/invisible-uv-pens/mar-c0-invisible-blue-uv-marking-pens/) (left figure, mre details [here](https://en.wikipedia.org/wiki/UV_marker)). UV labels can also be used to help finding the center of non-spherical particles, where Hough transformation for particle boundary detection does not work.
![wavelength1](uploads/c5f5bedd86d20079356f70581266e648/wavelength1.png)
## 4. Reference and further readings
[1] [Kollmer, Jonathan E., and Karen E. Daniels. "Betweenness Centrality as Predictor for Forces in Granular Packings." arXiv preprint arXiv:1807.01786 (2018).](https://arxiv.org/abs/1807.01786)
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